The present invention relates to the use of a precision displacement transducer for determining levels of liquid in a process vessel by mounting a magnetostrictive transducer onto the exterior of a sight glass having a liquid in communication with the liquid inside the process vessel, and a float that floats at the level of the liquid. The float contains a magnet that will provide a magnetic field that serves as the input signal for determining distances of the displacement transducer.
Various sight gage liquid level indicators have been advanced, including liquid level indicators that carry a magnet on the inside of a sight glass or tube, and which in turn cause a magnetically coupled indicator to move in a separate glass tube outside of the sight glass to establish a visual indication of liquid level in the process vessel. In some instances, the magnetic float has been utilized for continuous remote level transmission using electric signals that provide an output as a function of the float movement.
However, these products are imprecise, and do not provide an accurate continuous analog output of liquid levels for constant monitoring, and for inputs into various process controls.
While the magnetostrictive transducers have been used with floats that surround the sensing portions of the transducers, the present invention keeps all of the transducer components away from the process liquid while providing the benefits of precise and continuous indications of liquid levels.